Darwin's notes on Wallace's Island Life book

This is one of seven folios, written by Charles Darwin, making
comments on Wallace's book Island Life.

Darwin refers to specific pages of Wallace's text, giving
praise, opinion or suggestions for future editions, in a very
polite and gentlemanly manner. For example, Darwin asks 'is it not
rather rash to refer paucity of fossils to coldness of waters,
seeing how wonderfully rich the bottom of [the] sea has just [been]
found off the N. coast of Siberia, - not to mention the abyssal
regions of the great oceans. May not paucity be due to the stirring
up of the bottom by icebergs?'

Wallace made great contributions to the disciplines of
biogeography and animal distribution. The book Island Life focused
on speciation (the development of new species) in isolated
populations (islands). Wallace was one of the first scientists to
use geological events to explain certain aspects of distribution.
In the preface to the book, Wallace says he wrote Island Life after
four years' additional thought and research based on The
Geographical Distribution of Animals.

Wallace and Darwin had a good professional relationship and
corresponded regularly commenting on each other's work.